1. Field of the Invention
This invention relates generally to the use of metal ion-complexing compounds for flavor stabilization.
2. Description of Related Art
Fats and oils (of vegetable or animal origin) that find application in the food industry are perishable. They are subject to chemical changes, wherein the process of oxidation by the action of the oxygen of the air (autoxidation) is problematic, and in particular is accelerated by elevated temperature and by light. As oxidation products, there is enrichment primarily of decomposition products of oils/fats, which are composed substantially of short-chain carboxylic acids, aldehydes, alcohols and peroxides. Foodstuffs spoiled in this way are generally recognized by a quite unpleasant odor and/or taste, generally identified as rancid. Cool, dry storage of fat-containing products, as far as possible without access of air, increases their quality and stability.
Oils and fats are esters of the trihydric alcohol glycerol with linear aliphatic monocarboxylic acids (the fatty acids). These esters are called triacylglycerols. The fatty acids have considerable variability with respect to chain length and the number of multiple bonds. In particular, unsaturated fatty acids or TAG are affected by undesirable oxidation processes.
In the food industry, stability of flavor and taste is a problem with notable economic consequences. Often traces of metals and metal ions are involved in oxidative degradation reactions, which lead to the development of off flavors and thus contribute to the instability of the product. An attempt is often made to bind and/or inactivate any free metal ions that are present by adding complexing substances. In this connection, a number of complexing substances are known (e.g. ethylenediaminetetraacetic acid—EDTA), although their use is often subject to legal restrictions relating to foods.
The presence of metal ions has a promoting action on the oxidation process, as they support radical-based reactions. Undesirable oxidation is promoted in particular by iron ions.
TAG and fatty acids with multiply unsaturated fatty acids are particularly susceptible to oxidation, so that in particular these oils and fats or products comprising said oils and fats must be stored cool and should hardly be heated.
In particular, small molecules and oligopeptides, which specifically complex iron ions, are known to be natural iron carriers, so-called siderophores. These substances are formed primarily by microorganisms, but also by plants (phytosiderophores). The use of such compounds in food manufacture is already known; its aim is to suppress undesirable oxidation of fats by complexing unwanted metal ions, in particular iron ions.
Thus, in CA 2 457 993, methods are described in which the oxidation of lipids in foodstuffs is delayed by using siderophores and organic acids.
The use of natural antioxidants in foodstuffs is described in EP 2 149 308, wherein nicotianamine, a phytosiderophore, is used as a natural substitute for EDTA.
Antioxidants or extracts of bamboo leaves (so-called AOB), and their antioxidative and metal ion-complexing properties, are described In WO 2005/032275. Use as a food additive is said to block the autoxidation of lipids and bring about the chelation of transition metal ions.
The use of chelating compounds, for example citric acid, tartaric acid, gluconic acid and polyphosphates, for complexing iron ions in particular, is disclosed in GB 886,519.
A protective, antioxidative action of benzoic acid or benzoic acid derivatives is also known. For example, the antioxidative action of p-hydroxybenzoic acid and a plurality of methoxy- or hydroxy-substituted derivatives has been investigated (Natella F, Nardini M, Di Felice M, Scaccini C (1999) Benzoic and Cinnamic Acid Derivatives as Antioxidants: Structure-Activity Relation. J. Agric. Food Chem. 47, 1453-1459).